Jewel bearings for printer heads and the like

ABSTRACT

Jewel bearings for printer head assemblies and the like which are especially adapted for use in high speed printers of the dotmatrix type. A die-cast member is provided with a rear wall for mounting driving solenoids each having recipricating print wires extending from the rear wall toward the front wall thereof so as to be positioned to impact a paper document. Guide members are provided for maintaining the position of the print wires between the front and rear walls while enabling reciprocating action thereof. The guide members are provided with jewel bearings to maintain the alignment of the print wires while at the same time providing minimal wear even after long continuous and repeated use. The driving solenoids may also be fitted with jewel bearings. A front wall jewel bearing assembly accurately aligns the free ends of the print wires for reciprocating movement to reduce wear of the wires and to provide low frictional engagement with the inked ribbon.

United States Patent 1 1 Howard 1 1 JEWEL BEARINGS FOR PRINTER HEADS ANDTHE LIKE [75] inventor: Robert Howard. Roslyn. NY.

[73] Assignee: Centronics Data Computer Corporation, Hudson. NH.

{22] Filed: Feb. 11,1974

[21] Appl. No: 441.467

Related US. Application Data [62] Division of Ser, No. [79627. Sept. 13.1971. Pat.

[52] US. Cl. 197/] R; 308/36 [51] Int. Cl B4lj 3/06 [58] Field of Search197/1 [1.308/36. 101/93 C [56] References Cited UNITED STATES PATENTS2.129.065 9/1938 Loop 197]] R 2.674.652 4/1954 Johnson et a1. 197/1 R X3.108.673 10/1963 Green i 197/1 R 3.298.753 1/1967 Eaton 3118/363.467.232 9/1969 Paige... 197/1 R 3.584.575 6/1971 Distl 197/1 R X3.672.482 6/1972 Brumbaugh et a1... 197/1 R 3.679.273 7/1972 Cupler3118/36 FOREIGN PATENTS OR APPLICATIONS 364.273 9/1962 Switzerland197/43 1 1 May 13, 1975 Soffen [57] ABSTRACT Jewel bearings for printerhead assemblies and the like which are especially adapted for use inhigh speed printers of the dot-matrix type. A die-cast member isprovided with a rear wall for mounting driving solenoids each havingrecipricating print wires extending from the rear wall toward the frontwall thereof so as to be positioned to impact a paper document. Guidemembers are provided for maintaining the position of the print wiresbetween the front and rear walls while enabling reciprocating actionthereof. The guide members are provided with jewel hearings to maintainthe alignment of the print wires while at the same time providingminimal wear even after long continuous and repeated use. The drivingsolenoids may also be fitted with jewel bearings. A front wall jewelbearing assembly accurately aligns the free ends of the print wires forreciprocating movement to reduce wear of the wires and to provide lowfrictional engagement with the inked ribbon,

9 Claims. 14 Drawing Figures SHEET 2 OF 3 FATENTED W i 3 i975 JEWELBEARINGS FOR PRINTER HEADS AND THE LIKE This application is a divisionalapplication of US. ap plication Ser. No. 179,627 filed Sept. 13. I971now US. Pat. No. 1802.543, issued Apr. 9. N74.

The present invention relates to low friction bearings means and moreparticularly to jewel bearings for guiding slender reciprocating wireswhich may. for example, be used in high speed printers so as to maintainthe orietation of the reciprocating wires throughout their use while atthe same time significantly reducing wear.

BACKGROUND OF THE INVENTION Jewel members are typically used inmechanisms having moving parts wherein it is desired to reduce thewearing of such moving parts. It has been found that such techniques maybe used to great advantage in the rather widespread number ofapplications. However. such techniques have not heretofore been employedin high speed printers.

High speed printers of the dot-matrix type are well known in the priorart. A dot-matrix printer which has been proven to be quite successfulis described in copending application Ser. No. 37,8l5 filed May 15.1970, now abandoned in favor of copending continuation application Ser.No. 179,457 filed Sept. l0. l97l and assigned to the assignee of thepresent invention. The aforesaid application describes a printer headassembly for such dot-matrix printers which employs seven reciprocatingprint wires whose forward most free ends are typically arranged along animaginary vertical line at the print end of the one-piece die-castmember. Each ofthe print wires are reciprocated by an associatedsolenoid member mounted upon the rear wall ofthe die-cast member wherebyupon selective energization of the solenoids, the print wires are causedto impact a paper document (preferably through an inked ribbon). Byproviding a driving mechanism to move the print wire assembly across thepaper document it is possible to print any character number or symbolupon the paper document. Typically the print wire assembly is advancedacross the paper document and at five discrete closely spaced positionsthe print wire solenoids are selectively energized to form a seven byfive dot-matrix which is capable of representing any desired character,number or symbol.

The print head assembly is typically moved at a substantially constantrate of speed across the paper document necessitating the use of highspeed solenoids capable of driving their associated print wires toimpact the paper document and reset within a very short span of time soas to be ready to print the next vertical col umn of dots. In a printerof the type described hereinabove, the printing speed of a full line isusually of the order of more than 132 characters per second. Assumingfive columns make up each character, the print wires must therefore becapable of operating (i.c. impacting and resetting) at least 665 timesper second. The print wires which move a distance of approxi' mately 015inches of a necessity must be capable of being rapidly accelerated toprovide the desired impact force and be capable of being rapidlyaccelerated toward the reset position. Due to the rapid acceleration ofthe print wires (in both the printing and resetting direction) awhipping" effect is experienced by the print wires causing the wires tomove in a transverse direction and thereby frictionally engage the printwire guide means. This effect is especially pronounced near the forwardand rearward ends of the print wires so as to cause undue wearing ofboth the print wires and the guide means. thereby substantially reducingthe useful operating life of the printer.

BRIEF DESCRlPTlON OF THE INVENTION The present invention ischaracterized by providing jewel bearing assemblies for use in dotmatrix printers and the like in which guide means are provided foraccurately positioning the print wires near their forward and rearwardends while at the same time substantially reducing wear of both printwires and guide means to yield a print wire assembly having an extremelylong and useful operating life.

The present invention, in one preferred embodiment. is comprised of aone-piece die-cast housing having a rear wall for preferably thrcadedlymounting the forward threaded ends of a plurality of solenoid driversclustered together upon the rear wall in a rather compact fashion. Thesolenoid drivers are each mechani cally coupled to an associated printwire. The print wires extend through the rear wall and toward the frontwall and are arranged to converge together at the front wall of thedie-cast housing where they are aligned along an imaginary straight lineand arranged in very closely spaced fashion. A jewel bearing mounted inthe front wall of the housing effectively provides an extremely lowfriction guiding means for the forward free ends of the print wires aswell as eliminating any fric tional engagement between the forward endsof the print wires and the paper document (or inked ribbon) which mayotherwise occur even when the print wires are in the retracted positiondue to the close spacing between the front face of the printer headhousing and the paper document.

The portions of the print wires between the forward and rearward endsextend between the forward and rearward walls of the die-cast member andare gradu ally curved over this length. To maintain their curvature. atleast a pair of retainer plates are provided at spaced intervals withinthe die-cast housing. The retainer plates are provided with jewelhearing which are fixedly secured within associated apertures providedin the retainer plates. The print wires pass through the centralopenings in the jewel bearings to guide the reciprocating print wires soas to retain their curvature even during operation. The openings in thejewel bear ings preferably have throat portions located intermediate theopposing ends of each opening which are of a narrower diameter than theopposite ends of the openings, with the interior surface of the openingbeing a smooth curve so as to reduce friction. The narrower throatreduces the area of each jewel bearing which makes surface contact withits associated reciprocating print wire. thus minimizing the amount ofengagement therebetween and significantly reducing the wear of both thejewel bearing and the print wires.

The barriers may each alternatively be comprised of an intermediateplate provided with openings for re ceiving each jewel bearing memberwith the intermediate plate and the jewel bearing members beingsandwiched between a pair of retainer plates preferable spot welded tothe intermediate plate. Each of the retainer plates are provided withopenings having diameters aligned with the jewel bearing members andbeing smaller than the outer most diameter of the jewel bear ing memberso as to fixedly secure each jewel bearing member within the openingprovided for it in the inter mediate plate and between the pair ofretainer plates.

As another alternative embodiment the retainer plates may be providedwith openings for receiving hollow elongated guidc tubes. each of whichis adapted for receiving a reciprocating print wire. The ends of theguide tubes may each be provided with a jewel bearing which may befitted within an enlarged opening provided at the ends of each guidetube with the marginal lip of the opening being swaged so as to retainthe jewel bearing within the guide tube. Alternatively. jewel bearingsmay be fitted against the ends of the guide tubes and be retainedthereat by a cap means which telescopes over the end of the guide tubeso as to retain the jewel bearing in position As still anotheralternative embodiment, the retainer assemblies may be comprised of achannel shaped retainer plate for receiving and fixedly securing one endof a guide tube. A second retainer plate arranged a spaced distance fromthe channel shapped guide plate is fitted with a jewel bearing in eachof its openings which are retained therein by any of the techniquesdescribed hereinabove so as to provide a jewel bearing for each of theprint wires near the forward and rearward ends thereof.

In alike manner the solenoid assembly may be similarly fitted withjewelbearings either at the forward end thereof or at both forward andrearward ends so as to minimize wearing ofthe print wire within thesolenoid.

The front jewel which maintains the print wires in closely spacedfashion along an imaginary straight line is preferably formed of a pairof jewel members each provided with semi-circular grooves which arealigned so as to define circular shaped aperatures for receiving theprint wires. The jewels are accurately aligned relative to one anotherpreferably within ajig assembly and are joined together by channelshaped members so cured thereto by means of a suitable epoxy. Alternatively the channel shaped members may be replaced by a one piecerectangular frame into which the jewel bearing members are fitted and.after accurate alignment, are epoxied to the frame member.

The jewel bearing members described hereinabove significantly reducewearing of the print wires and the guide members (if used) as well asthe jewel bearing members themselves. while maintaining the desiredcurvature of the print wires during operation thereof so as to provide aprint wire assembly having an extremely long useful operating life evenafter repeated high speed use.

It is therefore one object of the present invention to provide noveljewel bearing arrangements for use in print wire assemblies and thelike.

Another object of the present invention is to provide a novel jewelbearing assembly for use in print wire aligning barrier plates tomaintain the spacing and curvature of a plurality of print wires evenduring operation thereof whiie at the same time significantly reducingwear even after long repeated use at high operating speeds.

Another object of the present invention is to provide guide means fittedwith jewel bearings for use in print wire assemblies and the like so asto provide a print wire assembly having a minimum amount of wear.

BRIEF DESCRIPTION OF THE FIGURES.

These as well other objects of the present inven tion will becomeapparent when reading the accompanying description and drawings inwhich:

FIG. 1 is a top plan view of a printer head assembly embodying theprincipals of the present invention.

FIG. la is side elevational view of the embodiment of FIG. 1 partiallysectionalized to facilitate an under standing of the apparatus.

FIG. 2 is an elevational view of a barrier plate assem bly which may beemployed as a substitute for those shown in FIGS. 1 and la.

FIG. 2a is an enlarged sectional view of a portion of the assembly ofFIG. 2 looking in the direction of Arrows AA.

FIG. 2b is an elevational view of the intermediate plate member of theassembly of FIGS. 2 and 2a.

FIG. 20 shows an alternative arrangement for the embodiments of FIGS. 2through 2b.

FIG. 21] is a sectional view of the embodiment of FIG.

FIG. 3 shows still another preferred embodiment of the present inventionemploying guide wires having jewel bearings.

FIGS. 40 and 4b show detailed sectional views of one free end of theguide wires in which two alternative arrangements for mounting jewelbearings are shown.

FIG. 5 shows an arrangement ofa solenoid employed in the embodiment ofFIG. I, for example, which is fit ted with jewel bearings.

FIGS. and 6b show two alternative arrangements for the jewel bearingmembers provided in the forward wall of the print wire assembly die-casthousing.

DETAILED DESCRIPTION OF THE FIGURES FIGS. la and lb show a printer headassembly I0 comprised of a one piece die-cast housing member II having apair of flanges 12a and 121) which extend to the sides of the housing aswell as extending below the housing and which are provided with openings13 for receiving suitable fastening members to secure housing 11 upon amovable carriage assembly (not shown).

The rear end of member 11 is provided with an upwardly projecting wall14 having a plurality of tapped openings 15 whose longitudinal axes arealigned so as to be substantially perpendicular to their associatedexterior surfaces 14a, 14b, 14c and Ma! shown in FIGS. I and la. Theopenings are aligned so that their longitudinal axes intersect at aremote point, which point lies on an imaginary line which is coincidentwith the central axis of opening 15'.

Each of the openings is tapped to threadedly engage the threaded collar17 of a print solenoid 18. Each of the solenoid assemblies are similarlyprovided with threaded collars for threadedly engaging an associated oneof the tapped aperatures IS (or I5). Each solenoid has a slendersolenoid wire 19 (or 19') projecting outwardly through an openingprovided at the forward end of each threaded collar 17, which printwires extend from the forward end of each solenoid assembly and throughthe hollow interior of the housing 11 so as to extend substantially tothe forward end thereof in a manner to be more fully described.

Die-east member 11 is further provided with a rear mounting portion 20comprised of inwardly directed projections 21 and 22 formed integrallywith the side walls 11a and 11b of die-cast member 11. Each of theprojections is provided with a narrow slot 21a and 220 respectively, forreceiving a substantially thin planar sheet 23 provided with a pluralityof openings, each adapted to receive a toroidal shaped jewel bearing 24.Sheet 23 is inserted within narrow slots 21a and 220 so that its bottomedge rests against the bottom surface 110 of diecast member 11 (see FIG.111). An epoxy is provided at 25 to retain planar sheet 23 in position.Each of the jewel bearings 24 are likewise epoxied as shown for exampleat 26 so as to rigidly maintain each of the jewel bearings in positionwithin the their associated openings provided in plate 23.

Die cast member 11 is further provided with a forward mounting portion27 comprised of first and second projections 28 and 29 extendinginwardly from side walls 11a and 11b and provided with narrow slots 28aand 290 respectively for receiving a thin planar sheet 30 whose oppositemarginal edges are fitted within slots 28a and 29a. The bottom edge ofsheet 30 rests against the base portion 11d of die cast member 11 and isepoxied as shown at 31 to retain the sheet in position.

Sheet or plate 30 is similarly provided with a plurality of openingseach receiving a jewel member 24 which members are epoxied as shown at32 so as to retain the jewel bearings within their associated openingsin plate 30.

The print wires 19 (and 19') extend forwardly from their associatedsolenoids so that each of the print wires passes through the centralopening provided in each of the toroidal shaped jewels, with the forwardfree ends of the print wires additionally being mounted to reciprocatewithin a final jewel bearing assembly 34 which, as was previouslydescribed, is positioned in very close proximity to a paper document andassociated inked ribbon so as to minimize frictional engagement with theinked ribbon (not shown for purposes of simplicity) and to prevent theprint wires from engaging the inked ribbon when in the retractedposition (i.e. the reset position).

It can be seen from FIGS. 1 and that the print wires (with the exceptionof print wire 19') are curved in the plane of both Figures. Due to theextremely high speed operation of the print wires, which wires arerapidly accelerated in the forward direction to impact the inked ribbonand paper document and are further rapidly accelerated in the rearwarddirection to return to the reset position, the print wires undergo awhipping effect whereby the portions of the print wires near theirforward and rearward ends experience movement or whipping in thedirection transverse to the direction of movement. The jewel bearingsserve to restrain their associated print wires from experiencing anymovement other than in the forward and rearward direction as well asproviding an extremely low friction engagement with the print wires soas to substantially reduce wear of the print wires near their forwardand rearward ends and thus provide a structure having an extremely longand useful operating life evan after repeated high speed use.

An alternative jewel bearing mounting arrangement which may be used inplace of that shown in FIGS. 1 and la is shown in FIGS. 2, 2a and 2b.Since the structure of the alternative barrier plate assembly issubstantially identical for both the forward and rearward assemblies 27and 20 shown in FIGS. 1 and In, only one such assembly will be describedherein for purposes of simplicity, it being understood that the onlydistinction between the two assemblies resides in the relative placementof the openings receiving the print wires and in the shape and outercontour of the barrier plate assemblies.

The barrier plate assembly 40 of FIG. 2 is comprised of an intermediateplate 41 which is shown independently of the other components in FIG. 2band is further comprised ofa pair of retainer plates 42 and 43 ofsubstantially identical size and configuration. The in termediate plate41 is provided with a plurality of openings 410 each of which is adaptedto receive a jewel member 24 as is shown best in FIG. 2a. The openings410 have a diameter substantially equal to the outer diameter of eachjewel member. The retainer plates 42 and 43 are each provided with aplurality of openings 42a and 43a respectively, with the centers ofthese openings being aligned with one another as well as being alignedwith the centers of the openings 41a and the central axes of the jewels24. FIG. 2a shows the arrangement wherein the centers of openings 42aand 430' provided in plates 42 and 43 and the center of opening 410 andthe longitudinal axes of toroidal shape jewel 24 all lie on a commonaxes represented by phantom line 45. The diameters of the openings 42aand 43a are substantially smaller than the outer diameter ofjewel 24 andare slightly greater than the inner diameter of jewel 24. To assemblethe structure of FIGS. 2 through 2b, the toroidal shaped jewels arefirst inserted into the openings 41a in intermediate plate 41. Plates 42and 43 are then positioned on opposite sides of plate 41 in a mannershown best in FIGS. 2 and 2a with all of the holes being in alignment.Preferable, the intermediate plate 41 is provided with a pair ofpositioning holes 41b and the plates 42 and 43 are provided with similarpositioning holes (only the positioning holes 42b being shown in plate42 for purposes of simplicity) whereby accurate alignment as between thethree plates is exactly determined. The plates are then joined togetherpreferably by spot welding at the points 46.

It can be seen that the width of plate 41 is substantially greater thanthe width of plates 42 and 43. The vertical marginal edges of plate 41are thus inserted within the narrow slots 28a and 290 provided in theforward projections 28 and 29 described hereinabove in connection withFIGS. 1 and la. The assembly 40 may be epoxied as shown at 31 in FIG. lato retain the assembly within the die-cast housing 11.

The rearward mounting assembly 20 is substantially identical to thatdescribed hereinabove with the exception that the retainer plates andintermediate plates would be of a larger size and would be provided withholes at different relative positions so as to maintain the gradual andsmooth curvature of the print wires along their entire length.

FIGS. 2c and 2d show a slightly modified arrangement from that depictedin FIGS. 2 through 2b wherein intermediate plate 41 is provided with asubstantially rectangular shaped opening 41a which is fitted with asheet 24' formed of the same material as jewels 24 which is drilled orotherwise machined so as to provide openings 240'. Sheet 41 is thensandwiched between retainer plates 42 and 43 in a manner similar to thatdescribed hereinabove, again preferably with the use of the alignmentpositioning holes so as to sandwich plate 41' and jewel sheet 24'between plates 42 and 43 in the manner shown best in FIG. 2c. Ifdesired, the positioning holes 24b may be drilled withing the jewelsheet 24' to assure alignment of the jewel sheet relative to theopenings provided in retainer plates 42 and 43.

As an obvious alternative to the arrangement shown in FIGSv l and la theplurality of openings provided in plates 23 and 30 may be replaced by arectangular shaped opening (or an opening of any other suitableconfiguration) into which a jewel sheet may be fitted and retained by asuitable epoxy. The jewel sheets would then be drilled or otherwisemachined so to provide openings at the appropriate positions FIG. 3shows a view substaintially simiiar to that shown in FIG. 1 wherein thebarrier plates 30 and 23 are provided with suitable openings forreceiving hollow tube guides 47, each of which extend between the frontwall Ile and the rear wall I4 of die-cast member II. The tube guides aresecured within associated openings provided in plates 23 and 30preferably by means of an epoxy provided for example at 48. Al thoughnot shown for purposes of simplicity, one such tube guide is providedfor each print wire 19.

Each of the tube guides are provided at their free ends with a jewelbearing arrangement which may take the form of that shown in eitherFIGSv 4a or 4b.

FIG. 4a shows one end of a tube guide 47 having a central opening 470.The outermost interior portion of central opening 470 is drilled orotherwise machined so as to provide a widened diameter portion 47!). Ajewel bearing 24 is fitted within the enlarged diameter portion asshown, preferably in a press fitted manner. The extreme end 476 of thetube is then swayed over the right hand end of jewel 24 so as to firmlyretain the jewel in position within the tube guide. It should beunderstood that either end or both ends of the tube guides may beprovided with jewel bearings in the manner shown in FIG. 4a.

FIG. 4b shows another alternative arrangement for affixing jewels to oneor both ends of the tube guides wherein a jewel 24 is fitted within theinterior of a cap 48 adapted to telescope over the end of the tube guide47 in the manner shown, The cylindrical portion 480 of the cap ispreferably force fitted over the associated end of the tube guide 47 andmay be retained thereon by spot welding, by the use of an epoxy, or anyother suitable material or securement technique. The cap 48 is providedwith an opening 4812 whose diameter is narrower than the outer diameterof the toroidal shaped jewel 24 so as to permit the free and unimpededpas sage ofa print wire through the central opening 24a of jewel 24while at the same time securing the jewel to the end of the tube guide.

Still another alternative embodiment ofthe invention is shown in FIG. Iwhich may be modified so as to employ the jewel bearings shown thereintogether with tube guides. In this embodiment. a channel shaped plate 50having, mounting surfaces 50a and 50b, is positioned in close proximityto plate 30 with the mounting surfaces 50a and 50b preferably being spotwelded to plate 30. The central portion 50c of plate 50 is provided withopenings for receiving and securing the forward ends of tube guides 47in the manner shown. As can be seen, the forwardmost ends of tube guides47 lie a slightly spaced distance away from the rearward ends of theirassociated jewels 24 thus providing separate securement means for thetube guides and the jewel members.

FIG. 5 shows a sectional view of a solenoid l8 comprising a one-pieceshell member 50 whose right-hand portion is substantially cylindrical inshape and is threaded at 17. A fastening nut 51 (note also FIGS. 1 andla) threadedly engages threaded collar 17 for the purpose of tighteningand locking the solenoid to rear wall 14 of the die cast member 11 oncethe solenoid is accurately positioned relative to the die cast member.The left-hand portion of shell 50 is also cylindrical in shape and has acylindrical wall 53 which defines a hollow annular shaped interiorregion 54 which houses solenoid coil 55. The central core portion 52 hasa centrally located opening 56 for slidably receiving print wire 19which is secured to the left-hand end of cylindrical shaped armaturemember 57 and which passes through a narrow diameter opening 56 to awider opening 56a and a still wider diameter opening 56b provided inshell 50. A tubular shaped wire guide 58 surrounds a portion of printwire I9 in the manner shown. The guide is preferably force fitted withinthe portion 56a of the elongated opening provided in shell 50. Asuitable dry powdered lubricant is preferably provided within theinterior surface of wire guide 58 to minimize wear during reciprocatingmovement of the print wire.

The armature member 57 which is formed of a permanent magnet material issecured to a disc-shaped member 61 formed of a springy or resilientmetallic material by means of a rivet 62. An end cap 66 retains thespring member between the interior surface of the end cap and the spacermember 65 in the manner shown. End cap 66 is tapped as shown at 67 so asto engage the threaded portion 68 of shell 50.

A jewel member 24 is fitted at the forward end of wire guide 58, whichjewel member may be secured thereto by either of the arrangements asshown in FIGS. 4a and 4b. If desired, the rear end 580 of print wireguide 58 may similarly be fitted with a jewel member in a fashionsimilar to that described hereinabove.

FIGS. 6a and 6b show two alternative arrangements for the jewel bearingprovided at the front wall He. Considering FIG. 6a, for example, thejewel assembly 34 is comprised of a pair of jewel sheets 34a and 3412each provided with a plurality of semicircular grooves 34c and 34d,respectively. The jewel members are aligned with their adjacent straightedges 34c and 34f, respectively, engaging one another and with thesemicircular portions arranged so that they cooperate to form circularshaped apertures. Preferably a jig means (not shown for purposes ofsimplicity) may be employed to maintain accurate alignment between thetwo plates. After alignment, a pair of C-shaped clips Cl and C2 arepositioned along the upper and lower edges respectively of the assy.Whereas the figure indicates the arms of the clips as being wider thanthe jewel sheets, it should be understood that the clips are preferablyarranged in very closely fitting fashion to the jewel sheets. An epoxyis provided between the engaging surfaces of the clips in the jewelsheets so as to firmly maintain a position the jewel sheets relative toone another.

The embodiment 34 of FIG. 6b differs from that shown in FIG. 6a in thatthe C-shaped clips Cl and C2 have been replaced by a rectangular shapedframe F. The assembly arrangement is substantially the same as thatdescribed hereinabove wherein an epoxy is provided within the region 343between the outer edges of the jewel sheets 34a and 34b and the interioredges of the frame F. Once the assembly 34' (or 34) has been completed,it may then be simply and readily epoxied into position within the slotprovided within the front wall lle of the one-piece die cast housing.

FIG. 7 shows a detailed sectional view of one preferred embodiment of ajewel 24. The jewel 24 is of toroidal shape and is provided with acentral opening 240 for receiving a print wire. The opening 24a has anarrow throat portion 24b arranged at a location intermediate the endsof the opening with the interior surface being gradually curved as shownso as to provide a smooth and gradual transition between the narrowthroat portion 24b and the widened ends of the opening 24a. Thisarrangement provides minimu] surface contact between the jewel bearingmember and its as sociated print wire. This arrangement is preferredwhether toroidal shaped jewel members are utilized or whether jewelsheets of the type shown by sheet 24' in FIG. 20 is employed so as tominimize both frictional engagement and wearing.

it can be seen from the foregoing description that the present inventionprovides novel jewel bearing assemblies for use in print solenoids andprinter heads wherein lateral movement of the print wires is minimizedwhile at the same time reducing wear of both the print wire and thejewels even after long high speed re peated use.

What is claimed is:

1. A movable unitary printer head assembly for use in impact printers ofthe dot matrix type comprising:

a housing having front and rear walls joined by a pair of side walls anda floor defining a hollow interior;

a plurality of print wire driving means secured to said rear walls; eachof said driving means including a print wire extending through saidhousing rear wall with their forward free ends extending through saidhollow interior and terminating adjacent said front wall;

spacing means secured within said front wall for maintaining the freeends of said print wires in a predetermined alignment;

first and second print wire positioning and guiding assemblies mountedin a stationary fashion at spaced intervals within said housing andadjacent said front and rear walls respectively;

jewel bearing means secured to said guiding assemblies and havingopenings each adapted to receive an associated print wire therethroughfor substantially restraining transverse movement of the print wires andmaintaining a plurality of said print wires in a predetermined patternto retain the gradual curvature assumed by the print wires between saidfront and rear walls while significantly reducing wear of said wireseven after long and repeated high speed operation and use, each of saidguiding assemblies being further comprised of hollow curved guide tubeshaving a toroidal shaped jewel member secured to one end of each guidetube; said guide tubes being secured to each of said spacing means.

2. The apparatus of claim 1 wherein said hollow guide tubes have anadditional toroidal shaped jewel member secured to the opposite ends ofeach guide tube.

3. The apparatus of claim 1 wherein at least one end of each guide tubeis provided with a circular recess having a diameter larger than thehollow interior of said guide tube;

said jewel member being press-fitted within said recess; the free end ofsaid tube adjacent said recess being bent inwardly around said jewelmember to main- 5 tain said jewel member within said recess.

4. The apparatus of claim I wherein at least one end of each guide tubeis provided with a recess having a diameter larger than the hollowinterior of said guide tube;

said jewel member being press'fitted into said recess;

an end cap being telescoped and pressf1tted over the free end of saidguide tube adjacent said recess; said end cap having an opening whosediameter is larger than the opening of said jewel member and smallerthan the outer diameter of the jewel member to retain said jewel memberin said recess.

5. The apparatus of claim 4 further comprising means for securing saidend cap to said guide tube.

6. A movable unitary printer head assembly for use in impact printers ofthe dot matrix type comprising:

a housing having front and rear walls joined by a pair of side walls anda floor defining a hollow interior;

a plurality of print wire driving means secured to said rear walls; eachof said driving means including a print wire extending through saidhousing rear wall with their forward free ends extending through saidhollow interior and terminating adjacent said front wall;

spacing means secured within said front wall for maintaining the freeends of said print wires in a predetermined alignment;

first and second print wire positioning and guiding assemblies mountedin a stationary fashion at spaced intervals within said housing andadjacent said front and rear walls respectively; jewel bearing meanssecured to said guiding assemblies and having openings each adapted toreceive an associated print wire therethrough for substantiallyrestraining transverse movement of the print wires and maintaining aplurality of said print wires in a predetermined pattern to retain thegradual curvature assumed by the print wires between said front and rearwalls while significantly reducing wear of said wires even after longand repeated high speed operation and use; said spacing means beingcomprised of an intermediate plate having a plurality of openings and apair of retainer plates each having openings aligned with one anotherand with the opening in said intermediate plate; said jewel bearingmeans being comprised of toroidal shaped jewel members each positionedwithin an associated opening in said intermediate plate;

said retainer plates being secured to opposite sides of saidintermediate plate and having openings whose diameters are slightlysmaller than the outer diameters of said jewel bearings to retain saidjewel bearing in said intermediate plate.

7. A movable unitary printer head assembly for use in impact printers ofthe dot matrix type comprising:

a housing having front and rear walls joined by a pair of side walls anda floor defining a hollow interior;

a plurality of print wire driving means secured to said rear walls;

each of said driving means including a print wire extending through saidhousing rear wall with their forward free ends extending through saidhollow interior and terminating adjacent said front wall:

spacing means secured within said front wall for maintaining the freeends of said print wires in a predetermined alignment;

first and second print wire positioning and guiding assemblies mountedin a stationary fashion at spaced intervals within said housing andadjacent said front and rear walls respectively;

jewel bearing means secured to said guiding assemblies and havingopenings each adapted to receive an associated print wire therethroughfor substantially restraining transverse movement of the print wires andmaintaining a plurality of said print wires in a predetermined patternto retain the gradual curvature assumed by the print wires between saidfront and rear walls while significantly reducing wear of said wireseven after long and repeated high speed operation and use;

said spacing means being comprised of an intermediate plate having acentral opening and a pair of retainer plates each having openingsaligned with one another and with the opening in said intermediateplate;

said jewel bearing means being comprised of a jewel sheet having aplurality of openings. said sheet positioned within the opening in saidintermediate plate; said retainer plates being secured to opposite sidesof said intermediate plate and having openings whose diameters areslightly larger than the diameters of the openings in said jewel sheetto retain said jewel sheet in said intermediate plate. 8. The apparatusof claim 1 further comprising a channel shaped member positionedadjacent one of said spacing means for securing one end of each of saidguide tubes adjacent said jewel bearing means.

9. The apparatus of claim 1 wherein at least one end of each guide tubeis provided with an end cap;

said end cap being telescoped and press-fitted over the free end of saidguide tube adjacent said recess;

said jewel member being positioned between the interior of said end capand one end of said guide tube;

said end cap having an opening whose diameter is larger than the openingof said jewel member and smaller than the outer diameter of the jewelmember to retain said jewel member in said end cap.

1. A movable unitary printer head assembly for use in impact printers ofthe dot matrix type comprising: a housing having front and rear wallsjoined by a pair of side walls and a floor defining a hollow interior; aplurality of print wire driving means secured to said rear walls; eachof said driving means including a print wire extending through saidhousing rear wall with their forward free ends extending through saidhollow interior and terminating adjacent said front wall; spacing meanssecured within said front wall for maintaining the free ends of saidprint wires in a predetermined alignment; first and second print wirepositioning and guiding assemblies mounted in a statiOnary fashion atspaced intervals within said housing and adjacent said front and rearwalls respectively; jewel bearing means secured to said guidingassemblies and having openings each adapted to receive an associatedprint wire therethrough for substantially restraining transversemovement of the print wires and maintaining a plurality of said printwires in a predetermined pattern to retain the gradual curvature assumedby the print wires between said front and rear walls while significantlyreducing wear of said wires even after long and repeated high speedoperation and use, each of said guiding assemblies being furthercomprised of hollow curved guide tubes having a toroidal shaped jewelmember secured to one end of each guide tube; said guide tubes beingsecured to each of said spacing means.
 2. The apparatus of claim 1wherein said hollow guide tubes have an additional toroidal shaped jewelmember secured to the opposite ends of each guide tube.
 3. The apparatusof claim 1 wherein at least one end of each guide tube is provided witha circular recess having a diameter larger than the hollow interior ofsaid guide tube; said jewel member being press-fitted within saidrecess; the free end of said tube adjacent said recess being bentinwardly around said jewel member to maintain said jewel member withinsaid recess.
 4. The apparatus of claim 1 wherein at least one end ofeach guide tube is provided with a recess having a diameter larger thanthe hollow interior of said guide tube; said jewel member beingpress-fitted into said recess; an end cap being telescoped andpress-fitted over the free end of said guide tube adjacent said recess;said end cap having an opening whose diameter is larger than the openingof said jewel member and smaller than the outer diameter of the jewelmember to retain said jewel member in said recess.
 5. The apparatus ofclaim 4 further comprising means for securing said end cap to said guidetube.
 6. A movable unitary printer head assembly for use in impactprinters of the dot matrix type comprising: a housing having front andrear walls joined by a pair of side walls and a floor defining a hollowinterior; a plurality of print wire driving means secured to said rearwalls; each of said driving means including a print wire extendingthrough said housing rear wall with their forward free ends extendingthrough said hollow interior and terminating adjacent said front wall;spacing means secured within said front wall for maintaining the freeends of said print wires in a predetermined alignment; first and secondprint wire positioning and guiding assemblies mounted in a stationaryfashion at spaced intervals within said housing and adjacent said frontand rear walls respectively; jewel bearing means secured to said guidingassemblies and having openings each adapted to receive an associatedprint wire therethrough for substantially restraining transversemovement of the print wires and maintaining a plurality of said printwires in a predetermined pattern to retain the gradual curvature assumedby the print wires between said front and rear walls while significantlyreducing wear of said wires even after long and repeated high speedoperation and use; said spacing means being comprised of an intermediateplate having a plurality of openings and a pair of retainer plates eachhaving openings aligned with one another and with the opening in saidintermediate plate; said jewel bearing means being comprised of toroidalshaped jewel members each positioned within an associated opening insaid intermediate plate; said retainer plates being secured to oppositesides of said intermediate plate and having openings whose diameters areslightly smaller than the outer diameters of said jewel bearings toretain said jewel bearing in said intermediate plate.
 7. A movableunitary printer head assembly for use in impact printers of the dotmatrix type comprisinG: a housing having front and rear walls joined bya pair of side walls and a floor defining a hollow interior; a pluralityof print wire driving means secured to said rear walls; each of saiddriving means including a print wire extending through said housing rearwall with their forward free ends extending through said hollow interiorand terminating adjacent said front wall; spacing means secured withinsaid front wall for maintaining the free ends of said print wires in apredetermined alignment; first and second print wire positioning andguiding assemblies mounted in a stationary fashion at spaced intervalswithin said housing and adjacent said front and rear walls respectively;jewel bearing means secured to said guiding assemblies and havingopenings each adapted to receive an associated print wire therethroughfor substantially restraining transverse movement of the print wires andmaintaining a plurality of said print wires in a predetermined patternto retain the gradual curvature assumed by the print wires between saidfront and rear walls while significantly reducing wear of said wireseven after long and repeated high speed operation and use; said spacingmeans being comprised of an intermediate plate having a central openingand a pair of retainer plates each having openings aligned with oneanother and with the opening in said intermediate plate; said jewelbearing means being comprised of a jewel sheet having a plurality ofopenings, said sheet positioned within the opening in said intermediateplate; said retainer plates being secured to opposite sides of saidintermediate plate and having openings whose diameters are slightlylarger than the diameters of the openings in said jewel sheet to retainsaid jewel sheet in said intermediate plate.
 8. The apparatus of claim 1further comprising a channel shaped member positioned adjacent one ofsaid spacing means for securing one end of each of said guide tubesadjacent said jewel bearing means.
 9. The apparatus of claim 1 whereinat least one end of each guide tube is provided with an end cap; saidend cap being telescoped and press-fitted over the free end of saidguide tube adjacent said recess; said jewel member being positionedbetween the interior of said end cap and one end of said guide tube;said end cap having an opening whose diameter is larger than the openingof said jewel member and smaller than the outer diameter of the jewelmember to retain said jewel member in said end cap.